Development of a Constant Current Water Bath Stunner for Poultry Processing

A Critical Review of Electrical Water-Bath Stun Systems for Poultry Slaughter and Recent Developments in Alternative Technologies

“…At the low voltage levels used in the United States, this period during which the electrical impedance breaks down could be extremely painful. Constant-current stunners, however, overcome this problem and are potentially able to deliver the maximum current in 0.25 s (Sparrey et al, 1993).…”

“…It is well documented in the scientific and trade literature that some birds can inadvertently experience painful electric shocks before making contact with the electrified water-bath (European Food Safety Authority [EFSA], 2004a; Gazdziak, 2007;Gregory & Bell, 1987;Schütt-Abraham, Wormuth, & Fessel, 1983;Sparrey, Kettlewell, Paice, & Whetlor, 1993). This can happen when a bird's leading wing makes contact with the water before the head or if wing flapping occurs at the entrance to the stunner.…”

“…These stunners control current flow through individual birds by electrically isolating Downloaded by [The University of Manchester Library] at 13:02 02 November 2014 each one to ensure that all birds in a multiple-bird, water-bath stunner receive the preset minimum current intended to achieve an adequate stun (Sparrey et al, 1993;Wilkins et al, 1999). However, because shackles are only 15 cm (5.9 in.)…”

“…Although commercial water-bath stunners generally operate on a constantvoltage basis, it is the current passing through each bird, rather than the voltage, that is important for inducing an effective stun (Sparrey et al, 1993). In constant-voltage stunners, especially those supplied with voltages not sufficient to cause immediate unconsciousness, there is a delay between the start of flow of electricity through the head and the actual stun because the applied voltage gradually breaks down the electrical resistance in the pathway.…”

“…In a constant-voltage, multiple-bird stunner, which is standard commercially, the total current equals the sum of the currents flowing though each bird individually (Sparrey et al, 1993). Variation in electrical resistance or impedance in the current pathway caused by natural variability among birds causes differences in the amount of current that individual birds receive as they pass through the water-bath (Bilgili 1999;Kettlewell & Hallworth, 1990).…”